A color cathode-ray tube (CRT) typically has an internal magnetic shield located within a funnel thereof to reduce the influence of magnetic fields on electron beam trajectories. The shield is usually made of cold-rolled steel and fastened to a shadow mask frame. A flexible contact spring sometimes is attached to the shield or frame to make electrical contact with a conductive coating on the inner surface of the tube funnel. An early method of attaching a contact spring was by welding.
However, the welding method often resulted in undesirable loose particles in the tube.
There have been several improvements suggested to overcome the problem associated with welding contact springs to either a frame or an internal magnetic shield. For example, U.S. Pat. No. 4,310,779, issued to Penird et al., on Jan. 12, 1982, and U.S. Pat. No. 4,433,267, issued to Kuryla et al., on Feb. 21, 1984, disclose contact springs that include a wrap-around clip that snaps onto a flute formed at the rear end of a magnetic shield. U.S. Pat. No. 5,126,624, issued to Ji, on Jun. 30, 1992, discloses a contact spring that includes a triangular type head that fits within a hole in a shadow mask frame. U.S. Pat. No. 4,670,686, issued to Muenkel et al., on Jun. 2, 1987, discloses a spring with a leaf tab and stiffening structure that is inserted through two opposed slots in an internal magnetic shield. Each of the foregoing contact springs includes one or more disadvantages. The simpler ones may work loose or move around too much, and the more complex ones are costly to manufacture. Therefore, there is a need for a contact spring with a simple design, which will be easy to insert and will not move around.
An improved contact spring is disclosed in U.S. patent application Ser. No. 09/149,320, filed on Sep. 8, 1998, by A. W. Bucher now allowed. The Bucher application claims a contact spring that includes a clasp with a hook and latch that can be snapped onto a land of and internal shield. It has been found that there are conditions that may even cause the contact spring of Bucher to disengage from an internal shield. The present invention provides an improvement in the type of contact spring shown in the Bucher application that prevents such disengagement.